If a ANSI 600 gate valve was initailly manufactured say for example in 1990, the maximum design pressure at 100 Deg F would have been 1440 psig.
However, now, API 6D reconizes that a ANSI 600 valve is rated for 1480 psig at 100 Deg F.
If I bought a used valve that was originally a 1440 psig...